This invention relates generally to exercise and rehabilitation apparatus and, more particularly, is directed to exercise and rehabilitation apparatus operative in isokinetic (voluntary) and passive (oscillation) modes.
Various exercising machines, such as those designated by "Universal", "Nautilus", "Cybex" and "Kin/Com", are well known in the art.
One of the first of these machines was the "Universal" exercising machine which uses a pulley-weight system, whereby the weights added to the pulley system can be varied by the user. With such apparatus, however, there are no controls over the manner, that is, the speed of movement and the torque applied by the user, in overcoming the weight load. It is only necessary that the user apply a force that is greater than the weight load through the pulley system. As such, the "Universal" apparatus is similar to a free weight system.
The "Nautilus" apparatus was developed to overcome some of the deficiencies of the "Universal" machine by providing a fixed path of movement of the respective arms thereof so that the latter follow respective paths designed for better muscle isolation during exercise. The "Nautilus" apparatus, rather than using a pulley-weight system, uses a novel cam arrangement. However, as with the "Universal" machine, the "Nautilus" apparatus does not control the speed of movement or resistive torque applied to the arm.
The "Cybex" apparatus, as exemplified in U.S. Pat. No. 3,465,592, recognized that the muscle is not equally powerful throughout its entire range of motion. The "Cybex" apparatus provides a motor connected through a gearing system to regulate the exercise arm of the machine so that it travels with a constant velocity, thereby taking into account the different strengths of the muscle during different angular extensions thereof.
Although the "Cybex" apparatus provides distinct advantages over the aforementioned "Universal" and "Nautilus" apparatus, the "Cybex" apparatus fails to provide necessary functions for truly accurate and corrective exercise and rehabilitation. In this regard, the "Cybex" apparatus uses a motor with two clutches. The arm of the apparatus is movable freely until the planetary speed of the gearing therein is reached, whereupon an impact resistive force is met by the user. This impact resistive force, of course, is undesirable, particularly from a rehabilitation standpoint.
Further, with the "Cybex" apparatus, although a constant velocity operation is provided for both extension and flexion of a muscle, there is no provision for controlled movement for both concentric and eccentric motions. The "Cybex" apparatus also only provides for voluntary constant velocity motions for a portion of its range of movement.
U.S. Pat. No, 4,235,437 discloses a robotic exercise machine which uses a computer to regulate the motion of an exercise arm in response to software programmed into the machine and in response to the force applied to the arm by the user as detected by a strain gauge at the end of the arm. By means of hydraulic cylinders and solenoid controlled valves, movement of the arm can be accurately controlled. However, the equipment provided in U.S. Pat. No. 4,235,437 is relatively complicated and requires expensive computer equipment and a complex linkage system. Further, because the equipment is computer controlled, the user must spend some time programming the computer with the desired settings before exercising. This, of course, is time consuming and detracts from the exercising.
It is to be appreciated that, with muscle exercise and rehabilitation apparatus, it is necessary that movement of the arm be smooth in all modes of operation. A problem with computer controlled apparatus is that the computer must make various samplings and computations, and thereafter makes corrections that are necessary. Although computer time is generally considered fast, the amount of time necessary for the computer to perform such operations and then control the mechanical and hydraulic devices of the apparatus may not result in smooth movement of the exercise arm, particularly at small loads.
There is also known a muscle exercise and rehabilitation apparatus sold by Chattecx Corporation of Chattanooga, Tenn. under the name "Kin/Com" which provides a computer controlled hydraulic system that monitors and measures velocities, angles and forces during muscular contractions. A load cell is provided to measure the force at the point of application, with an accuracy of 4 ounces. However, this apparatus, being computer controlled, suffers from the same problems discussed above with respect to U.S. Pat. No. 4,235,437.
U.S. Pat. No. 3,744,480 discloses an ergometer having a pedal driven DC motor as a load, including a frame for supporting the body of a person, whereby the pedals may be operated by either the feet or hands, and the electrical circuitry of the ergometer limits the load applied to the pedals as a function of work being performed, heart rate and increases in heart rate. However, with this Patent, the motor is used as a brake to provide a dynamic braking action. The problem with dynamic braking, that is, where there is a resistive load across the armature of the motor and the motor acts as a generator, is that such dynamic braking is not a linear function. As a result, it is difficult to accurately control the movement of the arm. Further, the range of operation with dynamic braking is limited. For example, dynamic braking can not be attained with a set velocity of 10 degrees/second in the 300-400 foot-pound range.
U.S. Pat. Nos. 3,848,467 and 3,869,121 each disclose an exercise machine in which a user applies a force to an arm which is coupled to a drive shaft, the latter being driven by a servo motor through a speed reducer. A brake is connected to the servo motor through the speed reducer, although in the embodiment of FIG. 3, a permanent magnet servo motor is used as both the powering means and the brake. A speed and direction sensor is connected with the drive shaft, the servo motor or the speed reducer, and supplies a signal to a comparator, corresponding the direction and speed of the arm. Another input of the comparator is supplied with a signal from a speed and direction programmer, corresponding to a desired speed and direction of movement of the arm. The comparator controls the powering means and the brake in response to these signals to regulate the system speed, responsive to varying exercises force applied to the arm during both concentric and eccentric muscular contractions.
With these latter Patents, however, the servo motor does not drive the arm for concentric muscular contractions, but only functions as a brake at such time, although it drives the arm for eccentric muscular contractions. Specifically, when the user grasps the exercise arm or bar, for example, during an arm curl operation, he first applies a force to move the bar to shoulder height, applying concentric muscular contractions, that is, where the bar is caused to move in the same direction that the force is applied. At this time, it is the user's force that moves the bar, and not the servo motor. As this force is applied, the servo motor functions as a generator. When the force is sufficient to cause rotation at a predetermined clamp velocity, a shunt element is connected in the circuit, to apply a dynamic braking force in opposition to and in proportion to the force applied by the user. The downward movement is performed by the servo motor. It is therefore clear that apparatus of this Patent suffers from the same problems aforementioned when the servo motor is used as a brake.
U.S. Pat. No. 4,184,678, although somewhat more sophisticated than the above two Patents, operates in the same general manner.
In order to overcome the above problems with the prior art, there is disclosed in copending U.S. patent application Ser. No. 676,493, filed Nov. 29, 1984, the entire disclosure of which is incorporated herein by reference, a muscle exercise and rehabilitation apparatus in which the servo motor is used to move the arm at all times.
Specifically, as disclosed therein, in the concentric isokinetic mode of operation, the arm is controlled to move with a regulated velocity in the direction of force applied by the user, for both flexion (bending) and extension (unbending) of the limb. For example, in a knee extension/flexion operation, where a cuff at the end of the arm is brought from a vertical to a horizontal position of the user, the servo motor which controls movement of the arm, is driven at a velocity dependent upon the force applied by the user, and in the same direction as the applied force, until a predetermined clamp velocity is reached. Once the predetermined clamp or set velocity is reached, the servo motor drives the arm at a predetermined constant velocity, whereby the arm moves with a constant velocity in the direction of force applied by the user. Thus, if the force applied by the user is too great, that is, will normally drive the arm at a velocity greater than the clamp velocity, the servo motor only drives and/or allows the arm to move at the predetermined clamp velocity. If the user stops applying the force, the arm will stop moving.
During the return movement, where the cuff is brought from the horizontal position to the lower vertical position, during flexion, the user must apply a force in the downward direction in order for the cuff to be moved downwardly. The servo motor moves the arm and the cuff, initially at a velocity dependent upon the downward force applied by the user. Once the velocity reaches a predetermined clamp velocity, the servo motor drives the arm at the predetermined velocity, whereby the arm moves with a constant velocity in the direction of force applied by the user. As with extension, if the user stops applying the force, the arm will cease moving with a constant velocity and come to a full stop.
Thus, with such apparatus, for flexion and extension, the servo motor drives the arm. The user does not move the arm but merely provides a measured force by which the servo motor is controlled.
In the eccentric isokinetic mode of operation, the arm is controlled to move with a regulated velocity in the direction opposite to the direction of force applied by the user, for both flexion and extension of the limb. In one embodiment, the range of speeds is much smaller than that in the concentric isokinetic mode in order to prevent harm to the user. However, again, for both flexion and extension, the servo motor drives the arm.
In the passive or oscillation mode, the arm is caused to oscillate by the servo motor at a constant speed, regardless of the force applied by the user. If there is a force applied by the user, regardless of the direction of such force (either concentric or eccentric), which would cause the arm to change its speed of oscillation, the servo motor controls the arm to maintain the constant speed.
In all of the above modes, it is the servo motor which moves the arm in response to the sensed velocity and/or predetermined force applied to the arm. The user does not move the arm. Because the servo motor is used to move the arm at all times, movement of the arm can be linearly controlled in response to the force applied thereto for forces within the range of 0-400 foot-pounds.
With such apparatus, circuitry is provided for limiting the angular range of motion of the arm. Specifically, for each direction, an amplifier receives a signal from a position sensor corresponding to the angular position, and a signal from a potentiometer corresponding to a preset angular limit. When the angular limit is reached, the amplifier provides an appropriate signal to a PWM amplifier which, in turn, controls the servo motor to prevent the arm from exceeding its set angular limit. The voltage across each potentiometer is set by a knob which the user adjusts to attain a desired angular limit. However, adjustment by such knobs is by a trial and error method, that is, the knobs are set and the user operates the apparatus. If the settings are incorrect, the knobs must be reset. Therefore, such adjustments may pose a danger to the user if the limits are initially adjusted for an excessive angular limit.
In the aforementioned copending U.S. patent application Ser. No. 676,493, a strain gauge is mounted on the arm and produces an output signal indicative of the load, which is used in the closed loop velocity servo system to regulate the angular speed of the arm. This is disadvantageous for the reason that, if different arms or arms are used for different purposes, each time that a different arm is used, the strain gauge would also have to be changed. This, of course, also requires that appropriate wires from each arm be reattached to the amplifier of the apparatus during each change.
The problems of sensitivity and vibration, however, are not limited to the mounting of the strain gauge on the arm. For example, due to inaccuracies in tolerances between connections of various mechanical elements, such as between the gear reducer and motor shaft, and between the arm and the gear reducer, leading to a looseness or backlash between such elements, causing servo instability which is inherently a problem with high gain systems. When this backlash is servoed through the controlled loop velocity servo system, inaccuracies in control of the arm result. Accordingly, it becomes virtually impossible to obtain stable large angular velocities, such as 450 degrees/second.
Still further, because of such backlash and decreased sensitivity, whereby large angular velocities can not be achieved, when it is attempted to, for example, kick at 450 degrees/second, the machine effectively prevents such angular speed. This may result in inaccurate or false readings from a monitor or the like, making it difficult to diagnose a problem of the user.
It will be realized that, in an apparatus which controls movement of the limb of a user by means of a servo motor, various errors in operation may occur, which may be dangerous and harmful to the user. It is therefore desirable to provide various safety features to overcome such contingent situations.